Such a simple question, but difficult as hell to answer. So many great songs out their for each instrument, but I'll try at least to name 1 of my favorites for each instrument (although there are probably many more for each).
Keyboards: Pyramaze - Melancholy Beast (This was probably the easiest. I'm not great on keyboard judging, but I particularly like Pyramaze's keyboarding, and especially this song.)
Drums: Evergrey - In the Wake of the Weary (Immensely powerfull, yet not overshadowing. Fucking masterpiece of a song and amazing use of drumming.)
Vocals: Evergrey - Obedience; Evergrey - The Masterplan (And also many others, but these definately one of the very best. Tom Englund is one of my 2 favorite vocalists, and in these 2 songs he sings so powerfully and with so much emotion, that it's just amazing.)
Lyrics: Dream Theater - A Change of Seasons (I still get goosebumps sometimes when I hear this song. The lyrics are very deep and emotional, and I really connect to some of it.)
I'm terrible at judging bass, so I didn't add that one. Also I couldn't choose one for guitar, because I don't think I possibly can. Great riffs, great solos, so many that are so different and so good. Impossible for me to pick one, or even some.